Two-stage continuous carbonization-activation process



Jan. 2, 1951 F'ild March 4, 1948 T. RM 5 Y mm W m R 0 W w a A M m a, m V N M I K Patented Jan. 2 1951 TWO-STAGE CONTINUOUS CARBONIZA- TION-ACTIVATION PROCESS Kenneth B. Stuart, Denver, 0010., assignor to The 7 Colorado Fuel & Iron Corporation, a, corporation of Colorado Application March 4, 1948, Serial No. 12,965

8 Claims. (01. 252-421) This invention relates to the method of producing activated carbon and has for its object certain improvements in the method of producing activated carbon of uniform high quality.

In the production of activated carbon, it is customary first to char carbonize suitable raw carbonaceous material and then to activate it, usually with a hot mildly oxidizing gas, such as superheated steam. To this end, the activating gas is passed into a column of previously charred carbonaceous material. The gas tends to channel its way through the column of char, following the line of least resistance, with the result that the char is not uniformly activated. In addition the gas tends to carry away suspended fines to an objectionable extent.

Investigation confirms my discovery that a method may be employed in which the carbonaceous material may be successively carbonized and activated, the steps of the process being so arranged as to assure substantially uniform distribution of the carbonizing and activating gases among the solid particles of carbonaceous material. In this way, each carbon particle receives substantially the same treatment. The carrying away of fines is also prevented.

In accordance with the invention, a continuous column of finely divided particles of carbonaceous material is progressively advanced through a carbonizing zone, a plurality of constricted passageways and an activating zone. The particles are moved relatively to one another as they pass through the carbonizing zone, constricted passageways and activating zone to effect their mixing. A plurality of small streams of hot activating gas under substantial positive pressure is released at a plurality of points distributed throughout the body of char confined in the activating zone to get a substantially even distri-' bution of the gas. Gas thus released is permitted to rise through the activating zone in contact with the particles of char to effect their activation. I-Iot gases in relatively small streams are passed from the activating zone While still under substantial positive pressure into the body of carbonaceous material confined in the carbonizing zone. Exhaust gases are Withdrawn from the upper portion of the carbonizing zone while maintaining the zones under substantial positive pressure.

To this end there is employed an apparatus comprising an upright retort with an inlet at the top for ingress of carbonaceous material and an outlet at the bottom for egress of activated carbon, the retort being divided into an upper carbonizing charring chamber and a lower activating chamber. A manifold with a top wall and a bottom wall is disposed laterally between the two chambers. An inlet extends through the wall of the retort and connects the manifold for the passage of activating gas into the manifold. A plurality of spaced upright conduits extend completely through the manifold for the passage of char from the upper chamber to the lower chamber, the ends of the conduits terminating at the top and bottom walls of the manifold to assure easy access of practically all of the char in the upper chamber to the conduits. A plurality of spaced and perforated down-pipes depend from the bottom wall of the manifold deeply into the lower chamber for the passage of gas from the manifold to the lower chamber. A plurality of spaced riser pipes extend completely through the manifold, the lower portions of the pipes depending downwardly well into the lower chamber and the upper portions of the pipes extending upwardly well into the upper chamber, the lower portions and the upper portions of the pipes being perforated so that gas in the lower chamber may 7 pass into the lower portions and be discharged through the upper portions into the upper chamber.

The upper end of the retort is advantageously provided with an automatic pressure controlled valve outlet for the controlled escape of exhaust gases from the upper chamber. preferably extends completely across the retort, thus forming the bottom of the upper chamber and the top of the lower chamber.

So that the carbonizing and activating steps may be conducted under pressure, the inlet at the top of the retort communicates with a charge chamber, a valve being disposed between the charge chamber and the inlet to open and close the passageway between the two. With an arrangement such as this, the valve may be opened to permit the passage of a charge of the raw carbonaceous materialinto the retort, after which the valve may be closed to prevent the escape of exhaust gases by Way of the charge chamber. Exhaust gases are preferably bled from the retort through the automatic pressure controlled valve outlet at the upper end of the retort.

The outlet at the bottom of the retort communicates with a cooling chamber, a valve being disposed between the outlet and the cooling chamber to open and close the passageway between the two. A star discharge is preferably located at the outlet to transfer activated carbon from the retort to the cooling chamber. With the valve closed, pressure conditions may be maintained Within the retort. From time to time the valve may be opened and the star discharge operated to transfer activated carbon from the retort to the cooling chamber, after which the valve is again closed to restore the desired pressure conditions within the retort.

Hot gases from the activating zone may be passed into the carbonizing zone in several ways. One is to pass them through the relatively small bodies of char in the constricted passageways. Another is to withdraw the gases from within the body of char in the activating zone at a plurality of points and to pass them into the carbonizing The manifold is lowered and the suspended fines are deposited. 1

These and other features of the invention-will be better understood by referring to the accompanying drawing, taken in conjunction with the following. description, in which lEig. 1 diagrammatically shows an apparatus illustrative of a practice of the invention; and .Fig. 2 is a section on the lime 2-2 of Fig. 1.

The .apparatus shown comprises a retort I!) having a heavy outer insulating shell II. The retort stands in an upright or vertical position and .is cylindrical in plan with a frusto-conical upper section !2 and an inverted frusto-conical lower section [3. The retort is divided into an upper or carbonizing chamber l4 and a lower or activating chamber 15. A manifold [6 with a top wall ill and a bottom wall [8 is disposed horizontally and fills the space between the two chambers. An inlet 19 extends through the wall of the retort and connects the manifold for the passage of activating gas into the manifold. A pluinto the lower chamber for the passage of gas from the manifold to the lower chamber. The number of down-pipes and perforations are such as to assure a substantially even distribution'of the activating gas in the body of char undergoing activation in the lower chamber. A plurality of spaced riser pipes 22 extend completely through the manifold, the lower portion of the pipes depending downwardly well into the lower chamber and the upper portionsofthe pipesextending upwardly well into the'upper chamben'the lower portions and the upper portions of the pipes being perforated so that gas in the lower chamber may pass into the lower portions of" the pipes and be discharged from the upper portions of the pipes into the upper chamber. Here again the number of pipes and their perforations-are such as to assure a substantially even withdrawal of exhaust gases from the char undergoing activation in the lower chamber into the lower portions of the riser pipes and a substantially even distribution of the exhaust gases in the carbon undergoing charring or carbonization in the upper chamber.

An automatic pressure controlled valve outlet 25 extends through the upper frusto-conical section of the retort to the exterior for the controlled escape of exhaust gases from the upper chamber. The outlet is preferably locatedabove the normal carbon level of the upper chamber so as to facilitate withdrawal of the exhaust gases.

The upper frusto-conical section of the retort terminates in an inlet 26 which connects with .a charge chamber 21 and a measuring bin 28, a valve Eli-being interposed between themeasuring bin and the charge bin.and a similar valve 30 being disposed between the'charge chamber and the inlet of the retort.

.The lower frusto-conical section of the retort terminates in an outlet 33 which connects with a charge chamber 34 fitted with an openable closure 35. --Inthe specific construction shown, a star ..dis-charge 36 is associated with the outlet of the retort to facilitate removal of activated carbon therefrom. A valve 31 is interposed between the star discharge and the charge chamber.

Theapparatus-may be employed as follows in carbonizing and activating suitable carbonaceous material:

Hot activating gas is passed through inlet. l9 into manifold l6, downwardly into and then out of perforated down -pipes 2 l,into lower chamber 15, into the lowerfportions vof perforated riser pipes 22, out ofthe upper portions of perforated riser pipes 22, into upper chamber 14. Some of the hot gas also passes from lower chamber 15 through conduits 26 into upper chamber [4. The gas accumulating in the upper chamber is suitably bled therefrom through valved outlet 25. Sufficient hot activating gas is thus passedinto and through the retort to bring it to and maintain it at a predetermined and optimum operating temperature.

The retort is filled with suitable raw carbonaceous material, such as finely divided anthracite coal. Valves 29. and 30 are opened and valve-3 and closure 35 are closed. 'The' coal is thenpassed through measuring bin 28 and,charge chamber 2? into retort 1 i3. As the coal tends to accumulate in upper chamber I some of it passes through conduits/2t until .lower chamber l5 is'filled. Coal is passed into the retort in this manner until upper chamber it is also substantially filled. Valves 29 .and'3l3 are then closed.

' The feeding of .hot gases into the system as described above is continued in order'suitably, to treat .the' coal. LIt will be clear that, as the activating gas escapes from perforated down-pipes 2 I, it is substantially. evenly distributed among the :particlesof coal in lower chamber I5. The partially spent gas passes through interstices-between adjoining particles until itenters the per forations of the lower portions of riser pipes 22 depending in'the' lower chamber. The. gas thus entering the riser pipes rises upwardly to the upper portions of the pipes from which it escapes and'is' substantially evenly distributed among the particles of'coal in upperchamber is. Some of the partially spent gas also rises upwardly through conduits 2e filled with coal particles. This, of course, aids in the even distribution of the gas throughout thebody of coal in the upper chamber. Exhaust gas accumulating under upper irusto-conical section l2'of the retort is'bled off through valved outlet 25 under controlled pressure conditions.

After a suitable interval; valve 31 is opened and star. dischargefifi is set in'operation to transfer treated coal from lower chamber 55 to cooling chamber 34. Valve 3'? is then closed and closure 35 openedor removed after a suitable cooling period to withdraw the treated coal; after which the closure is closed or returned.

,To replace coal or carbon thus removed from the. system, additional coal is passed into measuring. bin 28. With valve 3t still closed, valve 29 is opened and the coal transferred from bin 28 to charge chamber 2?. Valve 29-is then closed and valve, Stis opened to pass the coal from charge chamber 27 .to upper chamber I4 of the retort; after which valve 30 is again closed.

As a batch of activated carbon is removed from the lower chamber, an equal volume of charred coal drops from upper chamber I4 through conduits 29 into the lower chamber. A batch of raw coal is then fed to the upper chamber to replace that thus removed. In this way successive batches of material are passed through the retort by gravity as it is successively charred and activated.

Activating gases of various kinds may be employed. The most common are steam and carbon dioxide, or both. Activating gas may be obtained, for example, by burning combustible gas under pressure in air. The activating ste is conducted under positive pressure, that is, super- 1.

atmospheric pressure. This may vary over a rather wide range but should be substantial, pref erably in excess of 5 pounds per square inch gauge pressure. I have had excellent results with pressures in the neighborhood of pounds per square 1 inch gauge pressure. The pressure must, however, be consistent with safety, depending upon the strength of the apparatus.

Similarly, carbonizing gases of various kinds may be employed. It is economical to use the gases from the activating step for the carbonizing step, as described. It is also preferable to conduct the carbonizing step under a substantial positive pressure, say of the same order as in the activating step.

The flow of activating and carbonizing gases through the lower and upper chambers should be substantial and may, of course, vary over a rather wide range. I have, for example, passed activating gas in contact with the char at a temperature of about 1400 F. to about 1600 F. and at a rate of about 100 to 240 standard cubic feet of gas per hour per 1 to 2 pounds of activated carbon produced from the char; and carbonizing gas in contact with the carbon (Colorado sub-bituminous coal) at the rate of about 2500 to 6000 standard cubic feet of gas per to pounds of char per hour. Activation and carbonization of the carbon may be effected in a number of ways, such for example as described in my copending application Serial No. 501,044, filed September 3, 1943, now U. S. Patent 2,501,700.

It will be clear to those skilled in this art that the method of the invention lends itself to a number of useful modifications in practice.

I claim:

1. In the method of producing activated carbon, the improvement which comprises progressively advancing a continuous body of finelydivided particles of carbonaceous material successively through a carbonizing zone, a plurality of constricted passageways and an activating zone, the particles of char moving relatively to one another as they pass through the carbonizing zone, constricted passageways and activating zone to effect their mixing, releasing a plurality of small streams of hot activating gas under substantial positive pressure at a plurality of points distributed throughout the body of char confined in the activating zone to get a substantially even distribution of the gas, permitting gas thus released to rise through the activating zone in contact with the particles of char to effect the desired activation, passing hot gases in relatively small streams from the activating zone while still under substantial positive pressure into the body of char confined in the carbonizing zone, and withdrawing exhaust gases from the upper portion of the carbonizing zone while maintaining the zones under substantial positive pressure.

2. Method of producing activated carbon according to claim 1, in which hot gases from the activating zone are passed through the relatively small bodies of char in the constricted passageways into the carbonizing zone.

3. Method of producing activated carbon according to claim 1, in which hot gases are withdrawn from the body of char in the activating zone at a plurality of points and passed into the carbonizing zone.

4. Method of producing activated carbon according to claim 1, in which a portion of the hot gases is passed from the activating zone through the relatively small bodies of char in the constricted passageways into the carbonizing zone. and another portion of the hot gases is withdrawn from the body of char in the activating zone at a plurality of points and passed into the carbonizing zone.

5. Method of producing activated carbon according to claim 1, in which hot gases are withdrawn from the body of char in the activating zone at a plurality of points and released at a plurality of points throughout the body of char in the carbonizing zone to get a substantially even distribution of the gases.

6. Method of producing activated carbon according to claim 1, in which one portion of the hot gases is passed from the activating zone through the relatively small bodies of char in the constricted passageways into the relatively large body of char in the carbonizing zone; and another portion of the hot gases is withdrawn from the body of char in the activating zone at a plurality of points and released at a plurality of points throughout the body of char in the carbonizing zone to get a substantially even distribution of the gases.

7. Method of producing activated carbon according to claim 1, in which hot gases from the activating zone are released in a plurality of streams at a plurality of points distributed throughout the char in the carbonizing zone to get a substantially even distribution of the gases.

8. In the method of producing activated carbon, the improvement which comprises passing hot activating gas under substantial positive pressure through a body of finely divided char in an activating zone, releasing hot gases under substantial positive pressure from the activating zone in a plurality of streams at a plurality of points distributed throughout a body of finely divided char in a carbonizing zone to get a substantially even distribution of the gases.

. KENNETH B. STUART.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,413,146 Wheeler Apr. 18, 1922 1,502,592 Sauer July 22, 1924 1,563,295 Sauer Nov. 24, 1925 1,774,341 Von Halban et al. Aug. 26, 1930 1,865,667 Bailleul July 5, 1932 1,927,459 Krczil Sept. 19, 1933 2,166,225 Twining July 18, 1939 2,342,862 Hemminger Feb. 29, 1944 FOREIGN PATENTS Number Country Date 189,148 Great Britain Feb. 20, 1924 208,555 Great Britain Feb. 20, 1924 

1. IN THE METHOD OF PRODUCING ACTIVATED CARBON, THE IMPROVEMENT WHICH COMPRISES PROGRESSIVELY ADVANCING A CONTINUOUS BODY OF FINELYDIVIDED PARTICLES OF CARBONACEOUS MATERIAL SUCCESSIVELY THROUGH A CARBONIZING ZONE, A PLURALITY OF CONSTRICTED PASSAGEWAYS AND AN ACTIVATING ZONE, THE PARTICLES OF CHAR MOVING RELATIVELY TO ONE ANOTHER AS THEY PASS THROUGH THE CONBONIZING ZONE, CONSTRICTED PASSAGEWAYS AND ACTIVATING ZONE TO EFFECT THEIR MIXING, RELEASING A PLURALITY OF SMALL STREAMS OF HOT ACTIVATING GAS UNDER SUBSTANTIAL POSITIVE PRESSURE AT A PLURALITY OF POINTS DISTRIBUTED THROUGHOUT THE BODY OF CHAR CONFINED IN THE ACTIVATING ZONE TO GET A SUBSTANTIALLY EVEN DISTRIBUTION OF THE GAS, PERMITTING GAS THUS RELEASED TO RISE THROUGH THE ACTIVATING ZONE IN CONTACT WITH THE PARTICLES OF CHAR TO EFFECT THE DESIRED ACTIVATION, PASSING HOT GASES IN RELATIVELY SMALL STREAMS FROM THE ACTIVATING ZONE WHILE STILL UNDER SUBSTANTIAL POSITIVE PRESSURE INTO THE BODY OF CHAR CONFINED IN THE CARBONIZING ZONE, AND WITHDRAWING EXHAUST GASES FROM THE UPPER PORTION OF THE CARBONIZING ZONE WHILE MAINTAINING THE ZONES UNDER SUBSTANTIAL POSITIVE PRESSURE. 